Dont ask me why this is because it,s a while since I installed it,but on checking I find that KPT5 & KPT6 have sub folders within the Plug-in Folder called KPT5 & KPT6.However KPT3 lives in a sub folder called simply "Plugins"(all one word)within the main Plug-In Folder.There is no sub folder within this called KPT3,just the relivant files & yet it shows up fine as KPT3 on my filters list right ahead of the other two.As I say why it,s set up like this is now a mystery to me,but all the KPT filters (3,5,&6) are working fine.